If you want to map Moria, there is quite some research to be done.
To my knowledge no Tolkien's sketch is known even if I think it probable that there had to be one.
It would be a challenging project because Khazad dûm is unique - a symbiosis of rock and architecture. Huge staircases, statues, bridges above chasms, waterfalls, majestic halls ...

A kind of synthesis is :

"Khazad-dûm was a huge array of chambers, passages, mines, halls, stores and pits. In general, areas were either classed as mines or city. The mines were working sections of Khazad-dûm whilst the city was the area of habitation.

The city areas of Khazad-dûm were clustered primarily to the east; these were the oldest parts of the kingdom and had access to the Great Gates. They were structured into seven Levels and seven Deeps. The Levels stretched above the gate whilst the Deeps were set deeper within the mountain below the level of the East-gate. It is possible that the First Level (on which the Great Gates were set) and the First Deep were highly intertwined.

The eastern section of the city spaces had also been delved in such a manner as to have light shafts to illuminate their chambers. One example of this is the Chamber of Mazarbul which was located on the eastern edge of the Seventh Level.

The mine areas of Khazad-dûm were interlaced with the city spaces, but spread also westward toward the Doors of Durin. The mines ran deeper and further than any other tunnels within Khazad-dûm, and it is possible that more of the lower Deeps were given over to mining, although this is only conjecture.

The defined change between mines and city can be seen when the Fellowship pass through Moria - there is a marked difference between the early passages and chambers and those of the city structures illuminated by Gandalf.

Far below Moria, there are abysses, spaces and tunnels not known even by the Dwarves, but known by the Balrog. Unknown beings gnaw the earth and make them, far from the knowledge of any lore. "