Hi there,
You cannot move free space from D drive to your C drive without the help of third-party tools. You can either delete or move to the D drive files that are now on your C drive (which will thus create more space on the C drive).
If you are planning to clear up some space in the C drive then you can use the built-in Disk Cleanup tool which will clear out the spaces in the C drive.
https://support.microsoft.com/en-us/windows/disk-cleanup-in-windows-10-8a96ff42-5751-39ad-23d6-434b4d5b9a68
The other way around is to use some third-party tools like Easeus which might help you in transferring your free space from D to C drive.
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