$env:HETZNER_TOKEN = "<CLOUD-API-TOKEN>"
$env:HETZNER_SERVER_ID = "12345678"
$env:HETZNER_SERVER_TYPE = "cx23"
 
$body = @{
    upgrade_disk = $true
    server_type  = $env:HETZNER_SERVER_TYPE
} | ConvertTo-Json
 
Invoke-WebRequest `
  -Method Post `
  -Headers @{ "Authorization" = "Bearer $env:HETZNER_TOKEN" } `
  -Uri "https://api.hetzner.cloud/v1/servers/$env:HETZNER_SERVER_ID/actions/change_type" `
  -ContentType "application/json" `
  -Body $body `
  -UseBasicParsing
 
Remove-Item Env:HETZNER_TOKEN
Remove-Item Env:HETZNER_SERVER_ID
Remove-Item Env:HETZNER_SERVER_TYPE

https://docs.hetzner.cloud/reference/cloud#tag/server-actions/change_server_type