Now did the title confuse you? I’m sure it did!
Lets say you have three letters “ots” and you want to find all the words in the dictionary that contain those letters.
Well you can search for the words that contain those letters with a lookup tool I found online. http://www.menneske.no/ord/eng/vilkarlig.html
Just type in the letters you which to find in a word and the tool will find all the words which contain the letter combination you have entered.