A basic principle of good DAM is to not have multiple copies, but rather a single well curated source from which copies/derivatives are created when/if needed. Obviously, back-up copies will need to be made but these should be of a primary, curated resource.
Reading between the lines, you have 61k files that any/all of being: in the wrong place, badly organised or simply mis-filed.
I suggest you first make a watched folder of the existing file tree. Before ingesting records, consider whether you want keywords from the current path and set the app accordingly. Likely you don’t as the existing path isn’t the intended one for the long-term record. Plus, whilst the app can automatically create keywords from path at first ingest, if you move an asset the process doesn’t repeat nor are keywords from the defunct path removed (it wouldn’t be that easy in practice).
At this point you might want to take a copy of the catalogue if you’re keeping the old image set as it will still act as an index to that set.
Add a watched folder for the new location. Add sub-folders as required, as you go along. Drag existing records to the appropriate new watched folder location. If new & old folders are on the same volume, Portfolio defaults to moving the original, if different volumes a copy is the default. So, do experiment first and ensure your set-up and drag actions used work as you expect. You - according to your question, was copies in the new location.
When all records are copied, click on the root folder of the old watched set will will show the original set of 61k records. Select these and delete them - only the records! - then unwatch (remove) the old watched folder.
If using FDB catalogues, which don’t auto-compact, recover the catalogue to remove the space used by the previously 120k+ records. It won’t halve in size but should shrink noticeably. SQL catalogues don’t need this step.
If using screen previews, I’d test that the copied records have copied/created their previews. If not, regenerate them - via select items, Item menu , Regenerate thumbnails.
Lastly, don’t store 61k of files in one folder, as you appear to suggest was your final goal. The OS will allow to do that but it is sub-optimal for OS and Portfolio performance. It’s better to keep the number per folder in the 00s rather than 000s or more.