First of all, you should download and install ibmmq. Actually I don't know how to do it. But I hope that Google knows.
Then try to install PHP module with something like:
# apt-get install gcc make plesk-php73-dev
# /opt/plesk/php/7.3/bin/pecl install channel://pecl.php.net/mqseries-0.15.0
# echo "extension=mqseries.so" > /opt/plesk/php/7.3/etc/php.d/mqseries.ini
# plesk bin php_handler --reread
Then check that module is successfully loaded:
# /opt/plesk/php/7.3/bin/php -m | grep mqseries