Upgrade password hash in an existing system: Pbkdf2( salt , OldSha1Hash )
Yes, mostly

But wait, isn't SHA-1 broken?

It is. SHA-1 has collisions found as of 2017. But this isn't important for our usage, since we only require that SHA-1 won't collide for our inputs. Difference is that with 2017 attack attacker knows plaintext and tries to find another plaintext that gives same hash, in our case attacker doesn't know anything (not even hash). And we can assume that SHA-1 won't collide for real-life passwords, since if this was case it would be very major breakage of SHA-1 (that would have been found earlier).

There is however one catch: SHA-1 will limit your security to 80bits, since it has 160bit output and birthday attack can "limit security" to half of output bits (in our case). This is in fact reason PKDBF1 was abandoned in favor of PKDBF2, but most passwords are far from 80bits in security.

Note: I didn't take any of other problems into account in my answer. Choice of PKDBF2 might be considered outdated by this point too. I personally would suggest Argon2 (but some would call it too new to be adopted). Also PKDBF2 doesn't have one input, as others noted, but I'll assume it's just overlook.