Asking the user to select two items (which file & file format) before clicking download button

Question

I have a scenario where users can download report files. There are three types of files available in three different formats (.txt, .csv, .xls). I am giving checkbox for the types so that user can select all three types or at least 1 file to download, at the same time he should select the file format also.

Requesting you all to provide the best way to convey this requirement to the users. Any queries welcome.

P.S - the reports files are not listed in a table, just a pie chart representation of the whole summary is shown in the UI

Answer 1

This situation is exactly the same as selecting variations in an online store before shopping: the client select the variation type first and then click the Add to Cart button.