Old basic/expert series monsters convert simply and quickly. AC = 20 minus the old descending AC. Old AC of Zero becomes 20, 6 become 14, etc. Hit Dice go straight over (1d6 x hit dice). Hit Bonus is +1 per full hit dice level.
In game adventures, monsters will always be abbreviated like this:
Goblin (x3) (AC 13, HP 3, HB 0, DMG 1d6, MOV 50, MOR +5, XP 5)
AC Armor Class
HP Hit Points
HB Hit Bonus
DMG Damage
MOVE Move
MOR Morale Save
XP Experience Value
NEG Negotiation possible