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Well, since you used "UPR" in your topic's subject line, I am going to assume you are using UF and have a parameter file (*.upr).  Parameter files may contain multiple parameter sets that describe a fractal without storing the calculated pixels.  This file, along with the formulas, gradients, and other files, will allow you to render an image.

Once the image has been rendered, then just export it to the graphic format you wish to save it in.  And I believe this is where you would choose the .JPG format.  (You could save it as .BMP, .PNG, .TGA, etc....)
 
If you are not even sure how to get started with a UPR to produce an image, then open the Help file and under the CONTENTS, see the section titled Tutorials.  The following tutorials are available:

  •  Quick Start Tutorial
In this first tutorial, you will learn how to create a new fractal from scratch. You will experiment with formula parameters, add a coloring algorithm, and learn how to save and re-open fractals.
  •  Learning basic skills
This tutorial explains the basics of working with fractals: using Switch mode, zooming, and working with gradients to adjust colors.
  •  Working with layers
Now that you know the basics, learn how to add new layers, work with opacity and merge modes, and create transparent gradients.
  •  Learning about transformations
To make things even more interesting, this tutorial shows you how to add transformations to your fractals to create all kinds of different effects.
  •  Masking
The Masking tutorial extends the skills that you have learned so far and shows how to use the masking feature. Along the way, you will create a wonderful image to decorate your Windows desktop with!
  •  Working with animations
This final tutorial explains how to use the new animation features in Ultra Fractal 4. You will create a zoom movie, animate parameters, including gradient control points, learn how to use the Timeline tool window, and finally render your animation as an AVI movie.
 

Normally, Apo only opens the following file types for rendering:
  •  Flames (*.flame, *.flam3)
  •  FractInt IFS (*.ifs)
  •  Apo Parms (*.apo, *.fla)

Once the image information has been created, you would then have the option of Exporting to the .UPR format, so that it could be used within UF.