Regex help again (sorry, I am bad at these)

Sorry to have to ask the experts here for some regex assistance again. I am
admittadly awful with these and could use some help.

Have the following string (this is an example) that needs to be changed.
Need to use a search and replace because the links across over 200K records
are similar but not the same.

'<p>Complete the attached lab and submit via dropbox</p>\r<p><a href="
https://owncloud.porterchester.edu/HVACR/PCI_GasHeat/GasElectrical/HVACR1114_LAB_13A.pdf"
title="Lab 13A">Lab 13A<\a>'

Need the final string to separate the "LAB_13A.pdf" from the rest of the
URL by inserting a "&file=" in front of it. The final string should look
like:

'<p>Complete the attached lab and submit via dropbox</p>\r<p><a href="
https://owncloud.porterchester.edu/HVACR/PCI_GasHeat/GasElectrical/&file=HVACR1114_LAB_13A.pdf"
title="Lab 13A">Lab 13A<\a>'

I have tried something like:

update pcilms_assign set intro=regexp_replace(intro, '/([^/]*)\" title=$',
'&files=\1') where intro like '%https://owncloud.porterchester.edu%' and
course=18 and id=55413;

and the result puts the &file= in the wrong place (at the end of the whole
string).

Any suggestions?

Thanks!

-Chris