how can I make mytree interrain or biggerscale tree

I set max scale in option but plam is small I want to make it bigger or make my originalbigtree( in picture I want to make 20-30 feet plamtree but I can't)

if have video tutorials please give to me

alt text

Scale the tree up in your 3D app and reimport it, or increase the import scale in Unity and reimport it.