In 1981, TSR published the module D1-2: Descent into the Depths of the Earth. It was written by Gary Gygax and illustrated by David C. Sutherland III, David A. Trampier, Jim Roslof, Jeff Dee, Erol Otus, David S. La Force, and Bill Willingham. It consisted of a 32 page booklet and cover folder containing maps.
This conversion guide allows DMs to run the original module with 5th Edition rules and provides a reference sheet for encounters. It is intended for at least 6 characters of levels 12-14.
To use this conversion guide you will need a copy of "D1-2 Descent into the Depths of the Earth".