There are several things you could do here.
Let me inspire you with two of them.
1. Pattern the sketch feature
If you trim a single curve of the second sketch to the boundary of the first sketch (rectangle) then you can create the pattern as a feature pattern. In pattern feature you pattern the sketch with the single curve, while in the reuable references group you select the external refernece form the first sketch.
2. Project all the patterned curves to a sheet
If you want to contain the inner portion then you can create a sheetbody (extrude the rectangle over 0mm to get a sheet) and then project the curve pattern (the second sketch) to the sheet. The result will give you all the curves that are within the sheet boundary.