It's pretty easy. You can replace light or extra light DME with two-row. Same with pale LME. For amber extracts, thats a bit tougher since the amber extracts have other things in them besides base malt. If you take a look at the recipe (or if you want to post it here, we can help you), you can see what the recipe should look like.
Say the extract recipe has 80% extract, and 10% crystal and 10% other grains. You can keep the proportions the same, just using 80% base malt, 10% crystal, and 10% other grains. With amber DME, you'll probably want to use other than just plain two-row, but it depends on the recipe.
Broken Leg Brewery
Giving beer a leg to stand on since 2006