Assuming your Adwords account is connected to a Google Analytics property you can find this information on the 'Assisted Conversions' section of Analytics.
Conversions > Multi-Channel Funnels > Assisted Conversions
Near the top of the page you'll see a button which allows you to see data relating to all your traffic, or just your Adwords traffic - choose Adwords.
This will now show you a list of campaigns for your chosen date range where the campaign has been a part of the conversion process (as opposed to the Last Interaction attribution model that Analytics/Adwords defaults to) these are call Assisted Conversions.
It's worth reading up on Attribution models - this is how you choose which channel to give the credit for a conversion to. Example scenario below:
- User Googles a keyword and clicks a PPC ad, then leaves the site
- Same user then sees a Facebook post, clicks the link and converts
(this is an oversimplified example)
On a 'Last Interaction' attribution model, the conversion would be credited to Facebook. However if you were to use a 'First Interaction' model the conversion would be attributed to your PPC campaign.
There are a number of different attribution models (Last Interaction, Last Non-Direct Click, Last Adwords Click, First Interaction, Linear, Time Decay, Position Based) or you can create your own. There's no golden rule for attribution modelling, the best solution depends on your business. I personally use a customised version of the Time Decay model.
You can compare attribution models by going to:
Conversions > Attribution > Model Comparison