I believe this will be a 21 or 21A, the 21E does not have the "automatic" name on it, though it's very similar in appearance.
BTW - parts for these three are not all interchangeable, and getting parts can be very expensive. This is not a machine to buy if it needs parts, thinking you can fix it up cheaply. Best is to buy another that is in poor condition, but has what you need. Cams are also very hard to come by. Expensive if the seller knows what they have, and if cheap - pay for them with a poker face and don't smile until you have them out the door!
This is my husband's 21A
On the back - is the model number
Right above the number is a swing out door - where the cams go.
There is a lever you pull down to remove the cam
There are four cams, and each one has zigzag plus four stitches. A cam IS NEEDED to zigzag, but it does not matter which cam you have, so most often there is one in the machine even if it comes with no others. Check for this before you buy - or it's straight stitch only - and cams for this machine are very hard to come by. I've never seen them for sale on eBay except with a machine.
A Singer foot does fit, but I have no idea on sources for a 1/4" foot.
This is a hemming foot - it's what I had handy.
