How to get Certificate's Subject Public Key from CSR

Question

I am currently using this code to have the public key pinning

    OkHttpClientFactory okHttpClientFactory = () -> {
        CertificatePinner certificatePinner = new CertificatePinner.Builder()
                .add(domain, "sha256/" + pin)
                .add(domain, "sha256/" + pin_backup)
                .build();
        return new OkHttpClient.Builder()
                .certificatePinner(certificatePinner)
                .cookieJar(new ReactCookieJarContainer())
                .build();
    };

Here the pin or pin_backup is the SHA-256 hash of my Certificate's Subject Public Key.

How can I get that pin from a CSR? so that I can use it as a backup pin. Because that future certificate is not yet created, I only have a CSR for the same.

Update:

I am able to get the hashed pin using these commands on the CSR txt file.

Command to get public key from CSR:

openssl req -in csr.txt -noout -pubkey -out publickey.pem

Command to get the hashed pin from the public key:

openssl rsa -in publickey.pem -pubin -outform DER | openssl dgst -sha256 -binary | openssl enc -base64

I took it from here: