You need to use Library to sort all your images. It's easy to miss the filter in Library that permits resorting. It's located at the bottom of the central viewer in Library. First, go to the top of the screen and select View > Show Filter Toolbar. At the bottom of the viewer window, you should now see the filter toolbar. In the Sort field, click on the arrow and choose Capture Order or Added Order. Capture Order will list them by the data creation time in your camera. Added Order will list them in the order which you imported them into the Lightroom catalog. Note you can also click on the A/Z filter to reverse the order putting the most recent at the top of the screen. Note also that you can resize the previews using the Thumbnails slider at the bottom right of the viewer.
Once you've created this sort order, the filmstrip will be in this sequence in Develop.
If you need further help, please ask to schedule a lesson with me and I'll walk you through it.