This depends if you're using the on-premise or online version of D365.
If you're using the online version, then regular automated backups are taken of all your d365 environments. You can restore any of them depending on the type of environment going as far back as either 7 days (sandbox) or 28 days (production). You can also take manual backups of any of these environments. You should be able to get to these environments by going to admin.powerplatform.com (as long as you are an admin of your d365 environments)
Ref: https://docs.microsoft.com/en-us/power-platform/admin/backup-restore-environments
If you're running on-premise then the d365 databases would be sitting in a SQL server instance sitting on some machine in your organization or perhaps in your own azure instance that you would then have to manage the backup policies yourself
