I'm not sure what the best guidance would be. But, here is what I would do:
- Verify that my Time Machine backup looks ok. You should be able to explore the folders/files
- Copy over anything important from Windows bootcamp to an external drive of some sort
- Start the Mac in recovery mode https://support.apple.com/en-us/HT204904
- reinstall the MAC OS
- Restore Mac from backup https://support.apple.com/en-us/HT203981
- Finish restoration
- redo Bootcamp ensuring that my partitions are correct and that names ID my setup
- Reinstall Windows
- Create a new Mac time machine backup (your refreshed device will create a new backup, not update the previous one)
I'm not sure if there is a way to see the partitions in Windows; that would let you know if your Mac partition still exists. I'm also not sure how you may have erased content. One thing to check would be the size of the Windows c: drive. If it's very close to your actual hard drive size, you likely erased the Mac side somehow.
I might do a little more digging (look for things like view partitions in bootcamp, MAC OS missing after bootcamp, etc.) or wait and see if someone else offers a suggestion. I used bootcamp for one class in grad school 2 years ago so I haven't played around with it much outside of that.