Excellent that you're being offered Tadalafil - that's probably the best thing at this point. What dose are you getting?
Even if you can't get erections with the Tadalafil yet, the Tadalafil will improve blood flow around the nerves which may help healing, and in the penis which helps prevent damage caused by not having erections.
Depending on what dose you get, and assuming you were nerve sparing, the Tadalafil might help to get erections too, but it's too soon to expect much yet. If you can't get erections at 8 weeks post surgery (which most people won't), then it's worth asking for a pump too.
If you want to try having sex with an erection before you can get an erection naturally or with Tadalafil, you might find you can use the pump, or you might ask for a vasodilator drug, which are mostly self-administered penile injections.