How are you connecting the camera to the computer? Are you using Wi-Fi or a USB cable?
Are you building your own software? Or, are you trying to find an existing package to do this?
I was coincidentally just testing this with Wi-Fi using a custom application.
If you’re writing your own program, then create a loop for the custom filename.
example with psuedocode
arrayHoldingFilename = []
customPrefix = 'SQ'
startNumber = 100001
for i=0; i < maxFilesOnCamera; i++;
filePath = appDocumentsPath/ + customPrefix + startNumber + '.JPG'
arrayHoldingFilename.add(filePath)
You could also download the files and then run a script to batch change all the filenames.