@A.Elrayes, Thanks for posting in Q&A. To enroll iOS and MacOS devices, here are links with the detailed steps for your reference:
https://www.petervanderwoude.nl/post/getting-started-with-user-enrollment-for-ios-ipados-devices/
https://cloudinfra.net/how-to-enroll-personal-byod-macos-in-intune/
Note: Non-Microsoft link, just for the reference.
Please let us know if we have followed the above steps to enroll the personal devices.
For the caution to erase data, is one like this? If not, please get a screen shot to let us know it better.
Hope the above information can help.
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