Actually, BlockBench has an .MIMODEL Exporter addon inside it.
But the only problem is your model should be box UV so I will teach you how to change you models in to the box UV.
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Frist, select all your cube (CTRL+A)
Then, click the "Create Texture"(CTRL+SHIFT+T)
Choose your "Pixel Density" and tick the "Box UV" then Confirm
It will create a new texture, then save it
BlockBench isn't very smart, sometime you need to fix the UV by yourself
When everything is done you can export to .MIMODEL
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DONE