It depends on the shape that contains the 3000 square feet, if by linear feet you mean the boundary that contains it. You can't normally change square feet into linear feet without some picture of the kind of shape you are dealing with.

So a very skinny, long plot of land 1' wide and 3000' long will have a perimeter (boundary) = 1' + 3000' + 1' + 3000' = 6002'.

A square plot will have a boundary about 57'9" + 57'9" + 57'9" + 57'9" = 231'

So a very skinny, long plot of land 1' wide and 3000' long will have a perimeter (boundary) = 1' + 3000' + 1' + 3000' = 6002'.

A square plot will have a boundary about 57'9" + 57'9" + 57'9" + 57'9" = 231'