Backups for the purpose of migration from Montage to MODX need to be in X7U or X7L form. X7A is not a compatible format and cannot be read by MODX. Until Yamaha provides a free way to parse X7A files to generate X7L and/or X7U (which may never happen - so until forever) - the "new" recommendation for saving backups is to save X7U and make sure you keep track of your X7L files at load-time so you have backups of both X7A and X7U/X7L at any given time. The extra set of files (X7U/X7L) are for the off-chance you need to load your content on a MODX. Either out in the field (rented backline) - or because you later decide to switch keyboards and trade out/sell/get-rid-of your Montage.

If you have only X7A files - you would need access to a Montage to load them then generate X7L and/or XLU files.

As you load X7L and X7U files, your limit is 0.75GB less than Montage - so you may find you cannot have the same number of libraries loaded simultaneously. If everything fits within MODX's 1.0GB, you're fine.

Present MODX owner, previous Montag owner...

I loaded a bunch of drum samples and built my own kits, and backed them all up to usb. Trying to find a way to load them to my MODX.

The MODX will read your .X7U (MONTAGE User Files) and your .X7L (MONTAGE Library Files).