Adds Garrett's query for retrieving 8.15 knowledge

Author: benironside

docs/AI-for-security/knowledge-base.asciidoc

@@ -3,7 +3,27 @@
 
 AI Assistant's knowledge base feature enables it to recall specific documents and other specified information, and to use it as context when responding to your queries. This page describes how to enable and add information to knowledge base.
 
-NOTE: When you upgrade from {elastic-sec} version 8.15 to a newer version, information previously stored by AI Assistant will be lost.
+NOTE: When you upgrade from {elastic-sec} version 8.15 to a newer version, information previously stored by AI Assistant will be lost. Before upgrade, you can retrieve all stored knowledge using the following query:
+
+.Query
+[%collapsible]
+====
+GET /.kibana-elastic-ai-assistant-knowledge-base-*/_search
+{
+  "size": 10000,
+  "query": {
+    "bool": {
+      "must_not": [
+        {
+          "term": {
+            "metadata.kbResource": "esql"
+          }
+        }
+      ]
+    }
+  }
+}
+====
 
 .Requirements
 [sidebar]