Hi Retired to PA,
The stitch length knob on my 301A is the reverse/tack. Slide it all the way up to the top, that is reverse. It doesn't say it on the machine, but it does in the owner's manual.
Do you need a copy of the manual? I found it in PDF and can email it.
The light switch is up under the light hood near the bulb, just reach under like you are going to touch the base of the bulb, and you should feel a small twist knob, give it a turn.
I hope the knob hasn't been lost!
Good luck,
Aardie.