It's possible PAF ordered J-10CE with AL-31 as its condition for purchase due to possibly having more faith in Russian engine whether that is accurate and well reasoned or not. However this is but a rumor and J-10C models did use AL-31 so they can use those engines however the AL-31 will need to be ordered. Maybe China or Pakistan would need to place an order of 50 AL-31 engines from Russia if this is the case or maybe China can provide Pakistan with some left over AL-31 surplus if there are any which I doubt.
WS-10B has more thrust and is supposed to be more reliable than the old AL-31. CAC's factory building J-10C has been set up for WS-10B integration for many years already so I don't know how easy it would be for them to provide x number for PAF using older frame that is for AL-31. Maybe slightly used J-10C are the ones sold to PAF if that is the case.
Anyway this is rumor on top of rumor on top of some opinion, guesses, and more rumors. I think ToT on AL-31 however is a ridiculous rumor from messiach. This would require Russia agreeing to it which would also piss India off a lot. It would also be kind of pointless. Why would Pakistan want ToT on AL-31? It is nowhere near set up to build the engine under license or reverse engineer it. And if the purpose of ToT is simply for learning just so Pakistan can begin training some people in future roles for engine design, it is still hard to believe. It is more likely for China to give ToT and learning support for WS-10 and general high bypass turbofan technology including theory, design, and manufacturing. That would be delivered in a greater depth than any AL-31 ToT and it would also be more useful for Pakistan which would also be in China's interest if it can spare the time and energy for such a thing which I feel is highly unlikely.