SQL query based on datediff

Question

I am looking to construct a query using the ad exposure and conversion logs, I want to identify the ad exposure that gets "last touch" credit for the trial start. The conversion should have happened within 7 days after the ad exposure. Where Last credit means it was the last impression or click prior to conversion

This are my tables

ad_exposure_and_conversion

user_id	ad_id	Exposure Time	event_type
12368	574012	9/5/20 12:37 AM	Click
12368	574012	9/12/20 6:02 PM	Impression
12368	574012	9/13/20 5:53 AM	Impression
13953	449785	9/14/20 10:30 PM	Impression
17000	96336	9/1/20 11:29 AM	Impression
17000	96336	9/7/20 8:10 AM	Impression
17000	96336	9/10/20 9:43 PM	Impression
17000	96336	9/12/20 1:36 AM	Impression
22362	449785	9/2/20 5:41 AM	Impression
22362	449785	9/4/20 3:31 PM	Impression
22362	449785	9/4/20 6:05 PM	Impression
22362	449785	9/5/20 6:22 PM	Impression
22362	449785	9/7/20 3:48 PM	Impression
22362	449785	9/8/20 12:04 AM	Impression
22362	449785	9/11/20 6:00 PM	Impression
22362	449785	9/12/20 6:43 PM	Impression
22362	449785	9/14/20 6:05 AM	Impression
23437	96336	9/1/20 8:13 AM	Impression
23437	96336	9/2/20 6:14 PM	Impression
23437	96336	9/3/20 3:23 PM	Impression
23437	96336	9/3/20 10:06 PM	Impression
23437	96336	9/3/20 11:53 PM	Impression
23437	96336	9/4/20 8:07 AM	Impression
23437	96336	9/6/20 5:06 PM	Click
23437	96336	9/8/20 9:17 AM	Impression
23437	96336	9/8/20 10:32 AM	Impression
23437	96336	9/8/20 12:51 PM	Impression
23437	96336	9/9/20 1:30 AM	Impression
23437	96336	9/10/20 9:49 PM	Impression
23437	96336	9/12/20 6:27 PM	Impression
23437	96336	9/13/20 6:22 AM	Impression
23437	96336	9/14/20 3:39 AM	Impression

I dont quite understand the last credit part as I dont have ad experience. But this is what I have done so far

select ad_id
from ad_exposure_and_conversion
where DATEDIFF(DAY,a.Exposure Time,GETDATE() )>7 

Can someone share your thoughts