Welcome, and Mocha is adorable!!

Depending on how big she is, I would say a Beagle/Rottie cross, or if she is on the larger side, maybe a Coonhound (or Foxhound)/Rottie cross.
For sizing....Sadie, my foster Lab, was 11 pounds at seven weeks and she grew to be around 65lbs. My Collie/Aussie mix was 13lbs around 12 weeks and she is currently exactly 42 pounds at around a year (and yet she is almost the size of my 80lb dog...go figure).