Look closely at the rotor and it will have a spec for “last turning”.
That is not condemning limit, that is the narrowest allowed to put back on the car for one more set of pads.
Measure its current width, subtract groove depth x2. If that is lower than “last turning” depth, into the trash it goes. No one will turn it for you.
Otherwise price a new rotor and price turning this rotor. Small or popular rotors are often too cheap to turn.
Also turn or replace the other side; doing this NOT in pairs will make the car pull when you brake.
The old pads are junk. They may have been junk from day one. It won’t be worth having a machine shop grind the pads flat. And you don’t want a used pad face on a new rotor.
Tempting though it may be to scrimp, this is your brakes we’re talking about. And not even half your brakes; the fronts do 90% of the work when you really need em.