There are multiple ways of backing up TMv2:
a) You can perform a backup of the database directly through Microsoft SQL Server Management Studio. You may refer to MS SQL documentation on how to perform this. You can also get third party software to perform this for you on a schedule.
b) You can go to Fleet > Database backup (or Unit > Database backup if on a vessel installation) and click 'New' to perform a new backup. You will then have to select a destination for the backup file. This needs to be somewhere that is accessible via the user that the MS SQL Server service is running as. By default, this should include the TMv2Data folder as it should be shared with everyone.
There are also a number of settings available in System > Settings > Backup Settings. If you enable backup control, you can limit the amount of backups and send notifications if a backup hasn't been performed in the given time.
c) In System > Import and Export, you can click the 'Export All' button to create a SQL database backup. This has the same criteria as the database backup in point b).
You can also export all, or individual units, as v2z files. This exports the data from the tables into XML files and saves them in a v2z file which is essentially a .zip folder. You can rename a v2z file into a zip folder to explore the contents or extract specific XMLs. These exports do not include every table from the database, so some system settings such as TM Exchange settings will not be backed up this way.
v2z files can be imported by TMv2. This is the method used to create unit installations.