timemachine iphoto photo

i was upgrading to a new MacBook Pro from my time machine volume and something went wrong both my backup and the macbook were high Sierra latest builds something went wring and when I tried to make a 2nd attempt now my time machine volume can't be found is is on the drive but I can't mount it I...

We're greenhorns with Macs. We've just run Timemachine for the very first time and can no longer get to our pictures by iPhoto, nor find any other route so I can see them. I am presuming (or do I mean hoping!) the pictures are still there somewhere, either still on the Mac or the external...