Syntax error: word unexpected (expecting "do")

I am trying to create a script that renames all of my files within a directory hence the $( ls . ); by appending an incrementing number to the filename.

This is my script.

#!/bin/bash
# exercise 2

file_name=f
number=i
combined=$file_name" "$number

for f in $( ls . ); do
        echo $f
done

for i in {i=1; i=`expr $i + 1`}; do
        echo $combined
done

Although when I try running it with sh ex2. It gives me a Syntax Error of

sh ex2
ex1
ex2
script01
script02
script03
script04
script05
script06
12: Syntax error: word unexpected (expecting "do")