There is an old issue that when updating the plugin, you may lose some or all e-invoicing data post-update.
(this is an old issue, that should be fixed but we suggest this step just in case)
Backing up is not a complicated method, it simply means exporting your data as a spreadsheet file so you may reimport it at a later date.
instructions on exporting can be found in the "bulk updating" chapters of the following articles: