How do I translate microwave cooking instructions to fanless conventional oven instructions? I have a microwavable meal which instructs me to (for a 800 Watt microwave oven) perforate film and cook for 3 minutes on full power, then remove the film and cook for a further 1 1/2 minutes.

Unfortunately I don't have a microwave.

How do I convert these instructions so I can cook my food in a normal (no fan) oven?

How long should I cook for?

What (UK gas mark 0-9) oven setting should I use?
Lots of plastic are quite "transparent" to microwaves, but may turn really nasty when exposed to direct heat or the oven (the rest will turn nasty in microwave too; no such thing as oven-safe plastic...)  So, first step - move the meal to oven-safe dishes.

The expected time grows about x6; medium-high heat. Instead of "perforate the film" cover the dish. Remove the cover for the remaining time.

Also, for a lot of "ready to serve, just microwave it" dishes, a skillet is a better choice - unless the dish is "structured" like lasagna, you can get it hot when heating it in a skillet (stirring occasionally) in about 2-3 times the microwave time.