I am not sure why this thread is coming from the Dreamweaver Forum. Based on your previous Adobe Forum threads, I am assuming that you are still using Premiere Elements 12/12.1 on Mac computer.
1. You designate the frame rate and interlaced or progressive for a project using the choice of project preset (you do that manually or the project does it automatically).
2. If your question relates to still image duration...
In Edit Menu/Preferences/General, there is a preference for Still Image Default Duration. By default it is set for 150 frames. If you installed your program in the PAL TV Format, you are in a 25 frames per second system. So, that 150 frames is the equivalent of 6 seconds. When you open the project and import stills, all the stills that you import will have the 150 frames duration.
a. Important. If you change the preference from 150 to 180 frames (6 second to 7.2 seconds), only the stills that you import into the project after the change will have the 180 frames duration. All the rest that were on the Timeline before you made the change will remain the same 150 frames. Once that change is made, all stills that you import after the change from will have the 180 frame duration.
b. However, once you get the stills on that Timeline with the preference Still Image Duration set at 150 frames, you can change the duration of the still using Time Stretch. You right click the still on the Timeline, select Time Stretch from the pop up, and then change the duration from 00;00;05;00 to 00;00;07;00 (hours; minutes;seconds; frames).
Note that the preferences units are only in frames and the Timeline units give timecode style 00;00;00;00.
What I am not sure about is when you write
Each frame is coming in at about 2.5 min.
So, please clarify if your issue to pointing to frame rate in project settings or setting the still image default duration. Could your 2.5 minutes actually be 2.5 seconds?