How to hash/rehash tar files in a package with sha256 in a Bash script

I am trying to hash all the tarballs contained in a package with SHA256. Some of the tarballs have MD5 or SHA1 and I want everything to have SHA256.

#!/bin/bash

for dir in ~/path/to/package/*;
do
    if[-d "$dir"]; then
      dir1 = sha256 dir1.tar
      dir2 = sha256/location/of/know/packages/dir1.tar
      cmp dir1 dir2
    fi
done