How do I find the correct size command hook?

First of all, are the hooks that you have rated for the weight of the rod And the fabric of the curtains combined?

Secondly, what style of hooks do you have? There are many different kinds of Command hooks, some plastic, some metal. I have posted pictures below of the specific styles that are best suited to support curtain rods of your width.

Here is another tip to keep in mind when hanging curtain rods with any hardware.

To ensure that your rod is strong enough to avoid dipping in the centre, purchase a rod that has a minimum extension width equal to the width of the window.

For example, if your window is 48 inches wide, purchase a rod that extends from 45-58 instead of a rod that extends 36-48.

The picture below shows a rod that has extended too far to continue to to be strong throughout the width, resulting in it dipping in the centre, because it is the wrong size. A rod that does not extend so far; one that is double thickness for most of the width, should have been purchased.

Dipping in the centre will not only weaken the whole set up, it may even lead to the entire rod breaking in the centre, being pulled off the side hooks, and all the curtains come crashing down.

Thank you very much

You're welcome.

The hook style on the right in the picture is quite readily available at retail stores, depending on where you live. I have seen them in some grocery stores, and in some Walmarts.

I also just checked eBay; they have a big selection.

Here you go:

https://www.ebay.com/itm/4x-Heavy-Duty-Strong-Wall-Hanger-adhesive-Command-Jumbo-Hook-Curtain-Rod-Holder/183095760874?hash=item2aa15b97ea:g:xnAAAOSwPntcRqgj

https://www.ebay.com/itm/Command-Forever-Classic-Metal-Hook-Large-Brushed-Nickel-2-Hooks-FC13-BN-2ES/123737301530?hash=item1ccf51621a:g:0q4AAOSwVehctcL5

Thanks!