First, welcome to the forums.
Second, what you want to do can easily done with a program called automator, this program is already on your computer. Use spotlight or look in the applications folder to find it.
When you open automator, on the left is the library and that is all the actions you can perform. The applications folder should be expanded, if not then expand it. Then in the list of applications, select Finder then in the column just to the right will show the actions you can perform.
In the actions column select, "Get Specified Finder Items", then drag this action to the big column on the far left and it should add the action. The second action you need to find is the one called, "Rename Finder Items" and drag that under the far right action. It should have added an extra action called, "Copy Finder Items", this is good.
Ok now what you want to do is click the + on the very first action at the top, and you want to navigate to the folder with your pictures select all the pictures and hit open to add them to the window. Then you want to make a folder somewhere on your computer so when automator copies the images, it has a place to put them.
Then in the second action click the drop down menu and select "other" and navigate to the folder you just created, then click open to select that folder. Finally you are to the point where you decide what to name the files. Click the drop down menu and select, "Make Sequential" Then check the box that says "New Name", and you have to give the files a name. The rest is pretty self explanatory, when youre ready to run the workflow, click the play button at the top right.
Sorry this is a lot of text, but automator is a little odd at first and I thought a total walkthrough might help more than just saying, "use automator."