Help extracting alphanumeric string after matching pattern

[harishnpandey]

{"line":"2019-10-05 03:58:11.627 ERROR [xxx-csscsc0sssscs-xxxx] 1 --- [nio-8080-exec-2] c.u.f.b.s.registryImpl  : \u003c\u003c\u003c registryImpl  : registerInformation(): caught NnaException REGISTER_NOT_FOUND productId XA363636363633 requestDate 2020-07-24",

Need help to extract those productIDs (XA363636363633) which printed as REGISTER_NOT_FOUND in log

[gkapitany · Accepted solution]

search .. |rex field=_raw ".REGISTER_NOT_FOUND\s+productId\s+(?\w+)."

[harishnpandey]

Thank you very much . it worked with small modification as

search .. |rex field=_raw "REGISTER_NOT_FOUND\s+productId\s+(?\w+)"|stats count by regNumber