I want to make a stainless fuel line.My question is can I use an AN ferrule fitting? 3/8 if that matters.
Thanks in advance

The AN fitting system by definition is a flare style fitting, not a ferrule style. Just what are you trying, exactly, to do?

I want to make a fuel line with 3/8 stainless tube and I have some #6 AN ferrule fittings.Also I would like to use an electric fuel pump.

Better known as a compression fitting. Here's what Earl"s says:

Just make sure the ferrule fittings you're going to use are for stainless steel tubing. I had an awful time getting stainless steel fittings to stay sealed when I ran new lines on my efi Dakota, I ended up running all new plastic Fuel Injection lines.

If you are flaring the "ferrule" or sleeve is immaterial and they are interchangeable. More important is the tubing. Do not use seamless stainless tubing
for flaring. If you look down the barrel of your tubing and the inside diameter is not centered in the tubing it is seamless and will not flare properly and it will leak.
Welded and drawn stainless tubing is not easy to find these days.

If you are using a compression style fitting welded and drawn tubing and seamless are interchangeable.

The use of the word "ferrule" can be confusing, technically the fitting that the OP refers to is a compression fitting (bottom pic) where a ferrule is a sleeve used with flared tubing and a flare nut. (top pic)

There is also the Swagelok type fittings that are pricey but nice. They are available in a number of different materials, Won't leak, no flaring required, and are infinitely reusable if not abused.
I happen to have a bunch of SS ones on hand depending on what sizes etc. you might need. You can find their catalog online and get lost in there LOL

SWAGELOK the best , the juice is worth the squeeze