Can I change the destination folder for a backup ?

See Relocate iOS device backups. Review the rest of the Make a split library portable user tip for advice on organizing the library on external storage.

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Hello TnMtnMn,

Thanks for using Apple Support Communities! We see you're looking for how to back up your iTunes library to a different location, and we'd like to help.

This article has how to use an external drive to back up your iTunes library:

Back up and restore your iTunes library on your PC

Take care!