While one could do the 'march' that way, by 'moodle march' I meant upgrading the *site* ... like from 2.0 to 2.2.highest, then 2.2.highest, to 2.higher.highest. Notice that's 'site' ... the whole thing! It's what Moodle docs calls a migration:
https://docs.moodle.org/20/en/Moodle_migration
Backing up a course and then attempting to restore to a higher version of Moodle probably works best *IF* the higher version of Moodle is 'one or two up' - not 7 versions up - which is what you are attempting to do and having issues.
It would be best if you'd share information about your situtation ... some things about your server setup ...
How many courses are we talking about here?
Are you remotely hosted? If so, is your Moodle on a shared host? If so, who is provider? (SiteGround, GoDaddy, or other).
Is server Windows or Linux?
Do you have any addons to Moodle installed?
Before you begin a migration, make a site backup. Site backup consist of the code directory [*most important is the config.php file*], the data directory, and an SQL export of the DB for Moodle (called an SQL dump).
'spirit of sharing', Ken