How to find a specifically file(string) in deep Directory (file)

How to find a specifically file "hello.c"  in current deep Directory?

step 1:
tree|nl|grep hello
remember the number of the line
step 2:
tree|nl|less

How to find a specifically string "hello" in a file "demo.c"?

step 1:
nl demo.c|grep hello
remember the number of the line
step 2:
nl demo.c|less