You probably mean the Nano Media Card, which is Huawei's own standard and can only be used directly in their own phones. Previously, however, Huawei also supported Micro SD cards. This is no longer the case, if I have seen it correctly.
To your question though, the answer is simple and short: The Mate 10 Pro has NO memory card slot, at least not the versions here. So you have to make regular data backups to external media. Or use a cloud.