To determine how big the library is - right click library folder, select Properties, make sure you're on the General Tab and watch while it accumulates the size, e.g.
That is a library of ~3,500 books - at least 2 formats/book.
Probably not much point in compressing, many of the files are probably already compressed - the Export feature compresses anyway.
1 & 4 GB thumb drives are pretty small by today's standards - a 32GB drive shouldn't cost more than a couple of espresso coffees.
BR