You are going to want to update the switch port VLAN basically:
{{baseUrl}}/devices/{{serial}}/switchPorts/{{portNum}}
{
"name": "test from Postman",
"tags": "API",
"enabled": true,
"poeEnabled": true,
"type": "trunk",
"vlan": 1,
"voiceVlan": null,
"allowedVlans": "all",
"isolationEnabled": false,
"rstpEnabled": true,
"stpGuard": "disabled",
"accessPolicyNumber": null
}