SB5101 Certs on a SB6120

[sexyladynyc]

Hi! I have a SB6120 with forceware 1.4b1. I've been trying to get it to work for a few days with working certs from my sb5101 (faster speeds). I followed the tutorial on how to get the certs from the nonvol with cmnonexp.exe, rename them and then get them in the sb6120 via winscp.
Based on the tutorial rename them:
non01_public.key -> mfg_key_pub.bin
non01_private.key -> cm_key_prv.bin
non01_root.key -> root_pub_key.bin
non01_ca_cert.cer -> mfg_cert.cer
_cert.cer igual.

But my modem had:
fw_key_prv.bin <=
fw_cert.cer <=
root_pub_key.bin
mfg_cert.cer

Which is the right way to raname them? this is what Im getting in the log "Decrypt Auth Key: Couldn't format PKCS#8 private key into PKCS#1 format"
Thanks in advanced.