How to create footprint from shoe tread

So, I have this photo of my model and we'd like to add footprints from her boots to the ground. This isn't the exact background we're going to use, but it is pretty close! I haven't been able to figure it out myself and i haven't found anything to help me create a footprint from the bottom tread of the right boot. Any advice or tutorials i should check out?

Thanks in advance! 

I have the assets below if it helps.

1st is the sample background

2nd is just the model as a png

3rd is the rough idea put together without any footprints