toen means “when (in the past)”. Starts a sub-clause and sends its verb to the very end.
Subordinating · Onderschikkend
Toen ik jong was, woonde ik in Marokko.
When I was young, I lived in Morocco.
Hij lachte toen hij het hoorde.
He laughed when he heard it.
Drag scrambled words into the right Dutch order and master inversion and the verb-final rule.