Question

he used to sit on A bunch (nick out model o)

Answer 1

he used to sit on a bench is a sentence of past tense there is a use of modal called used to

Answer 2

$\huge\underline{\purple{\bold{Thanks}}}$Hey here is your answer...

He used to sit on a bench . it is the correct sentence...
it is a past tense sentence and the model is used too

Hope it's helps you..