[modeller_usage] Modelling of Homotrimeric protein without biological assembly

Actually I want to build a homology model of a human homotrimeric protein from a FASTA sequences. After BLAST I got a template which is 91% identical but it is originated from Mouse organism. and it is cryo EM structure.From there, I build a single monomeric chain of that human protein by Homology modelling. But it doesn't contain any biological assembly or asymmetric unit. So that, i am unable to build its trimeric structure. so, can you help me in two sections;1) how to build its homotrimeric structure?2) is there any way to generate the biological assembly coordinates from homology protein?Thanks in advance.Best regards.