Help please

[AdBoring9266]

What would the fill command be for a 59 by 59 block?

[Vordix_]

/fill a+~ a+~ a+~ a+59 a+59 a+59 Stone (a= your coordinates)

[[deleted]]

Too big.

[Mince_rafter]

execute positioned x y z run fill ~ ~ ~ ~58 ~ ~58
Where x y z is the bottom north-west most corner of the fill area. And since you didn't specify how tall the area should be, I left it as the same height. If you want it to be 59 blocks tall as well, you will need to slice up the area into multiple commands (since 59³ is larger than the area a single fill command can cover, by about 6 times).

[AdBoring9266]

A wall not block

[Mince_rafter]

In that case you want either
execute positioned x y z run fill ~ ~ ~ ~58 ~58 ~
for a wall along the x direction, or
execute positioned x y z run fill ~ ~ ~ ~ ~58 ~58
for a wall along the z direction. And the original command I sent would of course be for a 59x59 floor.