First time brewer here. Me and my girlfriend received a home brew kit for Christmas. The recipe called for 2 lbs of liquid malt extract and three lbs of dry malt extract. Along with hop pellets and a little irish moss. after putting the wort into the fermentation bucket and a week later I came to realize I mistook the 3 lbs of dry malt for 3 lbs of dextrose (corn sugar).also bubbling has ceased. Any suggestions or ideas on what we should do? are we going to get bottle bombs? Should we ferment longer? Please help!
No need to worry about bottle bombs as long as you let it finish fermenting. With so much sugar, the yeast probably lacked a lot of nutrients it would have otherwise normally gotten from malt, and it may taste a bit 'cidery' or 'champagne-y'. If you had caught it right away I'd probably have recommended adding some extra yeast nutrient to the fermenter to help minimize the stress on the yeast.
If it's only been a week, it's not too late to add some/half/all of the DME if you have room in the fermenter (just dissolve in as little water as possible, boil, cool and add) to try and add some more malt flavor to the beer, though it will dilute the hop character of the finished product. If you do this, you'll have to let this new sugar ferment for, say, another week. Do note that this will, proportional to how much you add, significantly increase the alcohol percentage of your beer, but might be worth it for the benefits to flavor. That's really up to you.
Otherwise, there's no harm to just bottling, drinking and chalking it up to experience.