Hi. As your skills are stronger in Cisco, follows the commands that are equivalent to Cisco in 3Com OS:
switchport mode trunk => 3com OS: port link-type trunk
switchport trunk allowed vlan => 3com OS: port trunk permit vlan
switchport trunk native vlan => 3com OS: port trunk pvid vlan
Regarding the LACP group (LAG = Link Aggregation Group), in 3com you need to create it as the following way:
link-aggregation group <lag_id> mode static
link-aggregation group <lag_id> description <description>
In the interfaces you want to group:
port link-aggregation group <lag_id>
To check the status of the LAG:
display link-aggregation verbose <lag_id>
HTH.