How can get all users by current user meta (array)?

This a:1:{i:0;s:1:"3";} is the serialized version of an array in PHP. You can unserialize it by using the function unserialize like below-

$data = unserialize('a:1:{i:0;s:1:"3";}');

So after unserialize inside $data you’ll get an array like below-

Array
(
    [0] => 3
)

This array will contain the user ID which is blocked by the user who is the owner of the user meta.

Now here you can run a foreach loop on $data and using get_user_by function you get all the users.

Hope that helps.