OK, just wanted to make sure that they were actually there before you deleted the ones off of your device.
So, the easiest way to delete a large number of photos is to go to the Photos option in the Photos app on the iPhone (left hand option on the bottom), then go into the "Moments" view in Photos. Once there, press Select at the top, and then go through eac of the dates in Moments, and press on the Select to the right of the date. This will select all of the photos for that date. You can repeat this for all of the dates you want to delete. Once you have selected everything you want to delete, click on the Trash Can in the bottom right-hand side of the screen.
If you see that you have deleted something that you did not intend to delete, you have 30 days to go to your Recently Deleted Album and recover it.
Best of luck,
GB