As @Bernhard Döbler has already pointed out this a regular RMV connection. Weekly ticket is 41 Euro, monthly is 140 Euro and yearly is 1377 Euro.
Try https://www.rmv.de/c/en/homepage and poke in your details.
From Frankfurt Main Station take the S3 (S-Bahn, local train). It goes every 30 minutes and takes about 20 minutes to Schwalbach Nord.
If you want to ...
You may find a useful article about public transportation in Amsterdam is quite extensive and I think covers basic knowledge to know for the first visit.
Metro and trains are well organized and there are maps if your phone would die. Amsterdam is not big and you can walk a lot especially if ...