trouble about salesforce cli "mdapi:convert"

hello, I am using salesforce cli tool.

I would like to use "sfdx force:mdapi:convert" command .

however,  result is "Component conversion failed.unable to get local issuer certificate".

I work in proxy enviroment.

I think it would cause about because the command is about to connect salesforce directry though I would like to connect via proxy.

Dose someone have any answer?