There are some food-tracking apps you can get--I think some are free for the more basic version. I know my H was using MyFitnessPal for a long time. It has lots of foods in the database (including packaged foods), and you can save common meals you have to enter them easily (like if you tend to have the same thing for breakfast). Also gives you a breakdown of carbs, protein, and fat, too. (I used it for a bit, but kept forgetting to enter stuff.)

It could be helpful to just track what you normally eat the first few days, just to get a sense of where you're getting the calories. Then figure out where to make changes. (I did that with drinking, though I got away from making changes for a bit--back on that now).