Hi i am installing mongodb6 in ubuntu 22 using docs but getting error

W: GPG error: MongoDB Repositories jammy/mongodb-org/6.0 Release: The following sign atures couldn’t be verified because the public key is not available: NO_PUBKEY 6A26B1AE64C3C388
E: The repository ‘MongoDB Repositories jammy/mongodb-org/6.0 Release’ is not signed .

getting above error when run apt update

i using this guide to install mognodb

how i can solve this