New in baking cakes, what is the measurement of one cup? cup measurement is confusing for me. please help?!

New in baking cakes, what is the measurement of one cup? cup measurement is confusing for me. please help?

Good question. A lot of new cooks, do not understand that there are two kinds of measuring tools. One for dry and one for liquid. Use a glass measuring cup for the one cup of milk. Set the glass measuring cup on your kitchen counter, and pour in the milk. It should reach the one cup, red line, marked on the glass.. Be sure and look at the line, at eye level to be accurate. For dry ingredients, like flour, use plastic cups, they come in 1 cup, 1/2 cup, 3/4 cup, etc. Dip the plastic measuring cup in the flour and level off the flour with the back of a knife.
When I got married, 53 years ago, I could not cook either. I got a Betty Crocker Cookbook, and I paid attention. The oven temperature, the time, being sure you mix the cake completely, this all counts toward making a good cake.
You will learn little things, as you cook. Like taking the eggs used in cake mixes, out of the frig, 30 minutes before mixing the cake. This lets them come to room temperature, and avoids any cold spots in the cake, as it bakes. This is all going to get easier and easier for you, and I just know you are going to be a really good cook. "God is in the Details."