you will need to make a lot adjustments. Dragon Mountain took low level creatures and had GM use them in way that would still be threat to high level pcs. hence the adventure set for level 16 characters. Trap creation, swarming/ over baring tactics and diving party tactics. 2ed does not convert over well to pathfinder because of this and other reasons. as may creatures had save or die effects in 2nd ed, limited use of healing, weaker healing, no feats limited amount of damage per round and attacks per round. Low level creatures could still be a threat to high level pcs. Enough to make them fear these lower level creatures. You will find if you did a one for one conversion of the creatures and traps the pcs breeze through them like they are not even there. They will end up short on xp at the end, for the bbeg and maybe under power or over powered depending on starting level of characters.
I went to do this adventure myself and just found it too much work especial since I used VTT for my gaming sessions. I would have had to compete create my own maps of the Mountain. I end up abandoning it and working on a similar even higher level adventure that a family member had wrote for 2nd edition since I could easily remake the rooms to the way I wanted them. I found myself having to completely replace\rebuild monsters, add hordes of them, or even add mythic rules because the monsters were not strong enough to even present a challenge to the pcs. You are also going to run into the same problem I did with Space having to make rooms vastly larger because 3.x edition bigger the creature the = harder so creature like giant emperor scorpions used to = to be large size and maybe 9 hit dice with death posion at -4 save. Now they are colossal in size and 17 hit dice. So if you have a room is 5 of those in it. you have to make that room almost 20 times the orignal size to have the same envorimental effect you would have had in the smaller room. Also the older creatures I would be more scared of the little ones then the big ones, while the big ones have a lot more hp and do more physical damage. The poison has become a joke in pathfinder. Same with disease and other status effects. They pose little or no threat to of party of equivalent level that is supposed to encounter said creature.
So while you can do a conversion it is going to be a lot of work to balance it out. Your basically committing yourself to a complete rewrite of the adventure with the exception of quest and story plot.
I think low level 2nd edition adventure scale a lot better for conversion and you will find a lot of people have done those on these boards and some of them are quite nice. But the high level ones require a ton of work.
