You can access the members of a collection by querying the database view APEX_COLLECTIONS. Collection names are always converted to uppercase. When querying the APEX_COLLECTIONS view, always specify the collection name in all uppercase. The APEX_COLLECTIONS view has the following definition:

COLLECTION_NAME   NOT NULL VARCHAR2(255)
SEQ_ID            NOT NULL NUMBER 
C001              VARCHAR2(4000)
C002              VARCHAR2(4000)
C003              VARCHAR2(4000)   
C004              VARCHAR2(4000)   
C005              VARCHAR2(4000)  
...
C050              VARCHAR2(4000)
N001              NUMBER
N002              NUMBER
N003              NUMBER
N004              NUMBER
N005              NUMBER     
D001              DATE
D002              DATE
D003              DATE
D004              DATE
D005              DATE
CLOB001           CLOB
BLOB001           BLOB  
XMLTYPE001        XMLTYPE
MD5_ORIGINAL      VARCHAR2(4000)  

Use the APEX_COLLECTIONS view in an application just as you would use any other table or view in an application, for example:

SELECT c001, c002, c003, n001, d001, clob001
   FROM APEX_collections
 WHERE collection_name = 'DEPARTMENTS'