@Stephen Marsh and it is a collection not a smart collection.
Just to be clear, I am talking of changing the path to image assets, not the collection or smart collection files. I think that Bridge will always be looking at C: drive for the collection or smart collection "library' files.
So if your actual image assets have changed from C to D...
AFAIK, you have two choices for a collection:
1) Delete and start again
2) Edit the .filelist file in a text editor
On Windows, as previously mentioned, the path to the file would be similar to (changing the username to your current computer user account name without spaces):
C:\Users\username\AppData\Roaming\Adobe\Bridge 2021\Collections
Note that the AppData directory is probably hidden and you will need to make hidden items visible. You can search the web for info on how to do this if you don't know how.
Once you find the collection that ends in a filename extension of .filelist (again, extensions may be invisible and you may need to change system settings to show known filename extensions).
In this screenshot, I am using notepad to change all occurrences of C: to 😧 drive:
