You were right Jose it was not installed.
But even after I install it, I got the following error again.
FO] DSpace RDF ......................................... SKIPPED
[INFO] DSpace RDF :: Local Customizations ................. SKIPPED
[INFO] DSpace REST :: API and Implementation .............. SKIPPED
[INFO] DSpace REST :: Local Customizations ................ SKIPPED
[INFO] DSpace SWORD ....................................... SKIPPED
[INFO] DSpace SWORD :: Local Customizations ............... SKIPPED
[INFO] DSpace SWORD v2 .................................... SKIPPED
[INFO] DSpace SWORD v2 :: Local Customizations ............ SKIPPED
[INFO] Apache Solr Webapp ................................. SKIPPED
[INFO] DSpace SOLR :: Local Customizations ................ SKIPPED
[INFO] DSpace OAI-PMH ..................................... SKIPPED
[INFO] DSpace OAI-PMH :: Local Customizations ............. SKIPPED
[INFO] DSpace Assembly and Configuration .................. SKIPPED
[INFO] DSpace XML-UI Mirage2 Theme ........................ SKIPPED
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 59.934 s
[INFO] Finished at: 2020-08-21T23:50:17+05:30
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.5.1:compile (default-compile) on project dspace-api: Compilation failure: Compilation failure:
[ERROR] /C:/dspace-6.3/dspace-api/src/main/java/org/dspace/authority/orcid/xml/Converter.java:[13,22] package javax.xml.bind does not exist
[ERROR] /C:/dspace-6.3/dspace-api/src/main/java/org/dspace/authority/orcid/xml/Converter.java:[14,22] package javax.xml.bind does not exist
[ERROR] /C:/dspace-6.3/dspace-api/src/main/java/org/dspace/authority/orcid/xml/Converter.java:[15,22] package javax.xml.bind does not exist
[ERROR] /C:/dspace-6.3/dspace-api/src/main/java/org/dspace/authority/orcid/xml/Converter.java:[38,13] cannot find symbol
[ERROR] symbol: class JAXBContext
[ERROR] location: class org.dspace.authority.orcid.xml.Converter<T>
[ERROR] /C:/dspace-6.3/dspace-api/src/main/java/org/dspace/authority/orcid/xml/Converter.java:[38,35] cannot find symbol
[ERROR] symbol: variable JAXBContext
[ERROR] location: class org.dspace.authority.orcid.xml.Converter<T>
[ERROR] /C:/dspace-6.3/dspace-api/src/main/java/org/dspace/authority/orcid/xml/Converter.java:[39,13] cannot find symbol
[ERROR] symbol: class Unmarshaller
[ERROR] location: class org.dspace.authority.orcid.xml.Converter<T>
[ERROR] /C:/dspace-6.3/dspace-api/src/main/java/org/dspace/authority/orcid/xml/Converter.java:[41,18] cannot find symbol
[ERROR] symbol: class JAXBException
[ERROR] location: class org.dspace.authority.orcid.xml.Converter<T>
[ERROR] /C:/dspace-6.3/dspace-api/src/main/java/org/dspace/statistics/util/DnsLookup.java:[41,10] reference to Record is ambiguous
[ERROR] both class org.xbill.DNS.Record in org.xbill.DNS and class java.lang.Record in java.lang match
[ERROR] /C:/dspace-6.3/dspace-api/src/main/java/org/dspace/statistics/util/DnsLookup.java:[41,23] reference to Record is ambiguous
[ERROR] both class org.xbill.DNS.Record in org.xbill.DNS and class java.lang.Record in java.lang match
[ERROR] /C:/dspace-6.3/dspace-api/src/main/java/org/dspace/statistics/util/DnsLookup.java:[45,10] reference to Record is ambiguous
[ERROR] both class org.xbill.DNS.Record in org.xbill.DNS and class java.lang.Record in java.lang match
[ERROR] /C:/dspace-6.3/dspace-api/src/main/java/org/dspace/statistics/util/DnsLookup.java:[69,9] reference to Record is ambiguous
[ERROR] both class org.xbill.DNS.Record in org.xbill.DNS and class java.lang.Record in java.lang match
[ERROR] /C:/dspace-6.3/dspace-api/src/main/java/org/dspace/statistics/util/DnsLookup.java:[69,22] reference to Record is ambiguous
[ERROR] both class org.xbill.DNS.Record in org.xbill.DNS and class java.lang.Record in java.lang match
[ERROR] /C:/dspace-6.3/dspace-api/src/main/java/org/dspace/statistics/util/DnsLookup.java:[73,9] reference to Record is ambiguous
[ERROR] both class org.xbill.DNS.Record in org.xbill.DNS and class java.lang.Record in java.lang match
[ERROR] /C:/dspace-6.3/dspace-api/src/main/java/org/dspace/statistics/util/DnsLookup.java:[80,14] reference to Record is ambiguous
[ERROR] both class org.xbill.DNS.Record in org.xbill.DNS and class java.lang.Record in java.lang match