#!/bin/bash
s='blahaaaaaa goog sdd 234 3242423
ala el-213123123123
1231231313123,141241'
tr "\n " "\r\n" <<< "$s" | sed -r '/[0-9]{10}/ s/[0-9]{3}/& /g' | tr '\r\n' '\n '
IyEvYmluL2Jhc2gKcz0nYmxhaGFhYWFhYSBnb29nIHNkZCAyMzQgMzI0MjQyMwphbGEgZWwtMjEzMTIzMTIzMTIzIAoxMjMxMjMxMzEzMTIzLDE0MTI0MScKdHIgIlxuICIgIlxyXG4iIDw8PCAiJHMiIHwgc2VkIC1yICcvWzAtOV17MTB9LyBzL1swLTldezN9LyYgL2cnICB8IHRyICdcclxuJyAnXG4gJw==