Hi @brittbosma
I may not have experience with switching from Tellent fo Personio but I am sure our Support team can help you with any hesitations or questions around this. A lot of ATS offer options to export data which then can be imported into Personio.
In this case, I would suggest you create a support request via Help & Feedback.
Help & Feedback > Browse for help > Contact us
Be aware that only Account Owners can contact our Support team. In case you are not registered as such, please contact your colleagues in the role, or add this information to your account. You can find out how here.
I wish you a lovely day.
Best, Roman