I don't think IPTC comes into it.
Select the folder etc as you have done
From main menu batch>options opens batch option box
Press 'batch process' tab
Adjust source and destination folders, check 'rename' box and press edit
This opens File naming box
If I understand what you want correctly, press 'none' on both sides, then required starting number. Then OK that and 'start' in Rename.
If you wanted to include eg Frampton in the file name, you would need to have done that by hand on the 1st file in the browser window, by clicking on it to highlight and rename; in that case use 'original name' in the File naming box & suffix new no

One reason for having .jpg s available is if you post to the/a forum you need a 200± kb file to post, the other is if you want to use either a slideshow function or browser in other progs to run through a number of pics, .nefs take a bit longer to unravel.