Its surprising that at this age you had undergo removal of teeth.
Ideally what we do with tooth having cavity is we restore
the tooth with dental cement if the cavity is nit deep.
If the cavity is too deep then also we can save the tooth by root canal treatment
followed by crown (cap)
when tooth is having deep cavity and have lost more than 80-90 % tooth structure along with poor gingival support then only we remove the teeth or else we can save it.
And having cavity is not a scary thing it happens only due to improper brushing technique, poor oral hygine.
If you undergo scaling (every 6 months) and maintain a good oral hygine then risk of developing cavities
will be much more reduced.