I've been running 3.0's "The Sunless Citadel" with great success. It's one of the best 1st level modules ever written (IMO and possibly others) and takes the PC's to 3rd.
One thing to note is that CR in 5e means something different than 3e/Pathfinder, in that the CR of a monster is the "high end" of its challenge versus an average encounter. Two CR 1/2 Hobgoblins means CR 1 in 5e, but this also means that, in a fair fight, at least one level 1 PC is going down (almost) guaranteed.
From Pathfinder specifically, I'd run Kingmaker... and I am running Kingmaker after The Sunless Citadel.
The Greyhawk Adventure path.
start with T1 and T2 skip T3-4 (they are junk)
add N2 as a sidetrek
goto A1, A2, A3, A4
with sidetreks of WG4 and WG5
Then hit S4
before committing to G1, G2, G3
D1, S1, D2, S2, D3
don't bother with Q1 it is .