Tamron zoom macro 1:4 for Nikon dslr?

I have a tamron zoom macro 1:4 lens and I wondered whether it would fit a Nikon d3100 or whether anyone knew of an adapter for it so it would fit?
This is really important because it decides what my next camera shall be

Added (1). I don't know what it was originally being used with but it is now with a canon ae-1 but with a lens mount converter
I know I won't be able to use the AF mode on the d3100 but will the lens fit and be compatible with it even if it needed a mount adapter?

What lens mount does it have now?

What brand camera are you using it on now?

Picking a camera system based upon already having a generic lens is sort of backward

Sort of like picking a sports car based upon the tires you already have.

Actually a zoom lens is not really a macro lens, but rather a zoom lens that can close focus.

Why?

A true macro lens is a special flat field, prime lens that can shoot calibrated image to subject ratios from 1:1, 1:2, 1:3 and 1:4.

If the Nikon D3100 is the camera you want, buy it and start building your new camera system.

It's probably the 70-300mm zoom which is misrepresented as a "macro lens." It will fit on without any problem, and you get automatic exposure. What you won't get is autofocus, as this lens doesn't have an inbuilt autofocus motor. The D3100 requires AF-S/AF-I standard lenses to give autofocus.

Alternatively if you want to use this Tamron lens, you'll want a D50/D70/D80/D90/D100/D200/D300/D600/D700…

It is is used on a AE-1 with adapter then I would guess it is a Tamron adaptall. You would need to source a Nikon adaptall mount.

To be honest a Tamron lens of that age is unlikely to match the performance of a D3100.To base your $600 camera purchasing decision around a 30yr old lens that is worth around $20 is a little odd to say the least!