I made a few changes to your script:

# !/bin/bash although it works is unconventional. Use #!/bin/bash instead.
Filename is one word but often we think it is two. Consequently it was spelled differently as file-name and file_name
Cosmetically lines between if -> else -> fi should be indented for greater readability. It still works vertically aligned it’s just easier to read when indented.
Extra words in Enter the name of the file can be shortened to Enter filename to make programs shorter and faster. This also makes it quicker for people to read instructions.

#!/bin/bash

echo -e "Enter filename: \c"
read filename

if [ -e "$filename" ]
then
    echo "$filename found"
else
    echo "$filename not found"
fi