This doesn't seem like a good situation/way to use masks.
masks normally are used for a quite large keyspace applied to a per-position pattern ... e.g. always 5 random alphanumeric characters at the start, followed by 3 lower-case characters .... or similar (an advanced brute-force technique, see wiki: https://hashcat.net/wiki/doku.php?id=mask_attack)
Maybe in this case you should better look into rule-based attacks (see wiki: https://hashcat.net/wiki/doku.php?id=rule_based_attack) based on a specific wordlist (base words).
masks normally are used for a quite large keyspace applied to a per-position pattern ... e.g. always 5 random alphanumeric characters at the start, followed by 3 lower-case characters .... or similar (an advanced brute-force technique, see wiki: https://hashcat.net/wiki/doku.php?id=mask_attack)
Maybe in this case you should better look into rule-based attacks (see wiki: https://hashcat.net/wiki/doku.php?id=rule_based_attack) based on a specific wordlist (base words).