certificates in DER fromat

Hi

We have a vendor that has supplied a cert in .der format, instead of the usual pem or cer formats

is there a way to convert to CER or PEM?

Kind regards, 

Stephen

(PS the interface is HL7 v2 over TLS/SSL)

Answers

Worked !

Microsoft Windows [Version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation.  All rights reserved.

D:\Certificates\>D:\InterSystems\HealthShare\bin\openssl x509 -in cacer
t.der -inform der -outform pem -out cacert.pem
WARNING: can't open config file: ././openssl.cnf

D:\Certificates\>