You can see a general overview of your course enrolment numbers using the Memberships page: What class a student is enrolled in for a particular subject
However, you may want to create a report that includes details of which bottom-level course a student is enrolled in for a given subject.
You'll need the General Admin: Export Data permission to create and manage your reports. If you don't have permission, you'll need to ask your admin team to give you permission using these instructions.
You'll add a new report column in Step 3 of creating your custom report, so you'll need to complete Steps 1 & 2 first.
When you get to Step 3, you'll need to add the Course Name (bottom level by subject) report column by clicking and dragging the column to the right-hand side.
On the slide-over, you can add the dates and the subject you want to report on.
You can add more columns to your report and continue through the rest of the steps to complete your report or select Skip Setup Wizard to skip to the last step where you can click Save & View Report.