Hello Ginza,
A 500 Internal server error will usually come as the script you are
running might have performed a illegal operation not permitted by that
server. For example Bluehost will give an internal server error when
file permissions are not safe.
In this case i will suggest either find what is causing the server to
return this error. Writing to your hosting company should get you a
list of causes which will help you troubleshoot.
Or easier way out, take a backup of the site, set it up on localhost &
then do the migration.
Parth