How to update DITA files

[Saara Tikkakoski]

I'm working on structured documents with Framemaker 2019 and I am unable to publish ditamap as html5 due to error which says to "validate xml source files". The person previously working on the same files using FM 2015. Now, someone in adobe support community said that it may be a problem of DITA versions, since FM 2019 works on DITA OT 3.0. and apparently the files that I have, are DITA 1.1. Not entirely sure about this, though. I am very much a beginner and don't really fully understand how dita workds. Anyway, how can I update my files to co-operate with FM2019 if DITA versions are the problem?

Sorry about the vague and vast question and thousand thanks for any advice or tips!