Hi,
The error means that the MySQL server that you are restoring on does not support the character set used by your database. WP from versions 4.2 onwards uses utf8mb4_unicode_ci by default, so the MySQL server needs to be able to support that, if you want to use a backup that was using that character set.
I'm not an expert on MySQL server versions, but this thread - https://stackoverflow.com/questions/29909290/collation-issue-is-it-possible-to-downgrade-convert-from-utf8mb4-unicode-ci-to - does say that MySQL 5.1 can't support utf8mb4_unicode_ci as a character set.
Best wishes,
David