Preparation for deployment ASP.NET Core 3 and 6 with Bamboo

[Rengga Okky]

Hello,

I am newbie here.

I already done to make build & deployment ASP .Net Framework with Bamboo and .Net Core 7 (newest Version).

But there's some code that using .Net Core 3 and 6 in the app.

when I use the current server to build the code, it comes with an error like this, 

error NETSDK1004: Assets file and error NETSDK1064:version 4.0.2 was not found. 

I think, that's because .Net Core 7 too high for the code that using version 3 and 6.

So what i need to do and prepare to build and deploy the source code that using .Net Core 3 and 6?

please help me A.S.A.P