Hi Carolmaggie,
Welcome to Apple Support Communities.
It sounds like you want to make all fonts larger and easier to read on your iPhone. The first article below explains how to increase font size in apps that support Dynamic Type, it sounds like you've already done this but there may be additional information in article that you're interested in. And, the second link below is for the iPhone User Guide, which describes the Zoom feature and walks you through enabling it.
iOS: Adjusting the font
http://support.apple.com/kb/HT5956
iPhone User Guide
http://manuals.info.apple.com/MANUALS/1000/MA1565/en_US/iphone_user_guide.pdf
Zoom
Many apps let you zoom in or out on specific items. For example, you can double-tap or pinch to expand webpage columns in Safari. There’s also a Zoom accessibility feature that lets you magnify the entire screen of any app you’re using. You can use Zoom together with VoiceOver.
Turn Zoom on or off. Go to Settings > General > Accessibility > Zoom. Or, use the Accessibility Shortcut. See Accessibility Shortcut on page 127.
Zoom in or out. Double-tap the screen with three fingers.
Vary the magnification. With three fingers, tap and drag up or down. The tap-and-drag gesture is similar to a double-tap, except you don’t lift your fingers on the second tap—instead, drag your fingers on the screen. Once you start dragging, you can drag with a single finger. iPhone returns to the adjusted magnification when you zoom out and in again using the three-finger double-tap.
Pan around the screen. While zoomed in, drag the screen with three fingers. Once you start dragging, you can continue with just one finger. Or, hold a single finger near the edge of the screen to pan to that side. Move your finger closer to the edge to pan more quickly. When you open a new screen, Zoom goes to the upper-middle of the screen.
While using Zoom with an Apple Wireless Keyboard (see Use an Apple Wireless Keyboard on page 27), the screen image follows the insertion point, keeping it in the center of the display.
I hope this helps.
-Jason