Cannot Find Base Price on Sales Order

Dear
Sales Order details cannot find Base Price with more one UOM

I made an Item "Wood", primary unit is EA. 1 EA is 0.2 M3. price with M3, 1 M3 = $1
So I doing this step :
1. I Made item with Primary : EA
                               Secondary : M3
                               Pricing : M3

2. Made Convertion : 1 EA = 0.2 M3
3. Create Item Branch/Plant
4. Create Price 1 M3 = $1

Now I Made a sales order with details  5 EA. but there is Error "Base Price Not Found"

I think base price not found because on UOM I use "EA" but price on "M3". how could automatic read from "M3"

Please Advice me

Thanks

Juned