This mod requires Fabric, not Forge.
As is visible in the dependencies section, this mod requires the Fabric API as well as Fabric Language Kotlin.
I also highly recommend that you install ToolTip AutoWrap because the tooltips in this mod include a description of the blocks and thus are quite long.
The Ender Box not only serves to move around hard-to-move blocks like chests, but it also reduces lag when placed around machines that do a lot of processing every tick or are complex to render.
To that end, the Ender Boxer allows you to automate the process of boxing and unboxing blocks to reduce lag when unused and still remain available for use when needed.