This post previously answers this question
Here is an email that I sent to another user having the same problem
emails block the sending of DLL files - even if they are zipped and renamed extensions - so I shared it here for you - hopefully you can get it from this location
Copy it to C:\Program Files\Trimble\Trimble Business Center folder - restart TBC and you should be good to go
If you ever need to find the file on your PC it should be installed here at this path - Windows Explorer may not find it (it did not for me either but it is there)
C:\Program Files (x86)\Trimble\convertToRINEX
Let me know that you got it sorted out and that you are good to go
Alan