what places do the imprint fossils form?

Answer 1

In sedimentary rocks.

Answer 2

If you mean fossil tracks (like dinosaur tracks) or traces, also called ichnofossils. They form in mud, or sand mixed with lime during an unconformaty or hyatus (when sediment deposition stopped briefly between tidal impacts), which turnes into limestone and sandstone when it hardens within hours or days. Fossil tracks are fomed in a matrix similar to cement which hardens rapidly. The preservation of tracks and trackways has to be covered in a short time or they would be destroyed. Some tracks are covered by volcanic ash, or softer mud or sand which sometimes hardens into stone. Then rock layers are formed over that. Later erosion exposes the harder natural cement track layer. I have found dinosaur tracks in Arizona, California, Utah, Texas, and Wyoming. And discovered unknown tracks in Coconino in Arizona and Georgia. And I have some bird trackways from Wyoming.