Where is the data saved after a form is submitted?

Where are they stored? This is about as much details Microsoft gives:

https://techcommunity.microsoft.com/t5/microsoft-forms-blog/microsoft-forms-is-gdpr-compliant/ba-p/251515

https://support.office.com/en-gb/article/data-storage-for-microsoft-forms-97a34e2e-98e1-4dc2-b6b4-7a8444cb1dc3

Forms from staff who leave the company, either transfer ownership to a group prior to leaving or admins can follow this https://support.office.com/en-us/article/transfer-ownership-of-a-form-921a6361-a4e5-44ea-bce9-c4ed63aa54b4?ui=en-US&rs=en-US&ad=US if the owner has left the organisation already, transferring the ownership by using a special URL which displays their forms:

Admin section for Forms, this tells you how to access available settings - https://support.office.com/en-gb/article/administrator-settings-for-microsoft-forms-48161c55-fbae-4f37-8951-9e3befc0248b.