I went on the Dose Adjustment for Normal Eating course and was told 3-4 hours, also not to test/correct before then to see if my levels had come back into range, with CGM's we can become too fixated on rising BG levels, but this is where we have to become more relaxed and not obsess over an arrow going straight up, to this point I think CGM's can be anxiety inducing if we let them, we simply just have to acknowledge and be patient.
Different foods will deliver different reactions as pointed out already, fat delays carb absorption so a pizza high can hit you 3+ hours later, whereas a low carb, high protein can cause a steady long rise.
As a newly diagnosed I would write down your BG levels before each meal and to track them on this basis, your insulin requirements will change over the months but this is a good way to chart what's going on against what's been eaten and will help you and your team decide if your insulin doses need adjusting.