Access ctx value of transactional data from Marketing instance

I am sending transactional emails to clients.

we need to target the client after 3 days from marketing instance so I need to access the data inside the CTX. but the issue is ctx is not visible in query (using nms:eventHisto). when we use steps like using data extract and linking the Data Extract directly with the Data Loading activity, the ctx parameter becomes empty even though it is visible in the interim population.

How to retrieve the ctx parameter value from the marketing instance. Please help.

@_manoj_kumar_ 

@costa_n11 
@bisswang 

@vraghav 

@shrawansaxena-1