What have you tried to rename your files this way, and what as the error message? Renaming the files as you describe should be possible. E.g., using a rename string like so {filenamebase}_{caption} if you want/need you could trim the maximum length of the caption too.
However, perhaps your way of renaming the images is not the best to really get them organised. For instance, you likely end up with many duplicate file numbers, resulting in files from different dates ending up sorted together (sure, you can have PM sort by e.g., capture time, but that is slow).
Another disadvantage is that if you ever change the caption you need to rename the file too.
I suggest you take a different renaming approach, one which already reflects your organisation strategy better and sorts your images in a way that helps you find them.
Personally I rename all my files so they automatically sort by date. My personal images I organise by year and "event", my professional images by client and commission. The renaming part is automatic (done at ingest), the further organisation is, of course, manual, but easy to do.
The renaming string I use looks something like this {datesortlong}_{timesortlong} this will produce unique, sortable filenames if you shoot with one camera. Because I shoot with multiple cameras at the same time, I have actually added the camera model to this filename to always keep it unique, even if two cameras fired at the exact same time. I could have added e.g., the serial number too, but one of my cameras didn't embed that in the metadata so I thought of another simple solution. As I do not own multiple cameras, the camera model sufficed in my case. (I abbreviate the camera model to e.g., just D4 instead of NIKON D4 using a code replacement for brevity).
Hope this helps,
Hayo
