For reasons I don’t want to get into, I’ve had to locate all PST files on a number of workstations. Plugging this one line Powershell command into our RMM, I was able to see what workstations had what files and upload them to Office365 for safe(r) keeping. 

gci -path c:\ -recurse -include *.pst -erroraction 'silentlycontinue'|select-object fullname,lastwritetime | fl fullname