What does it mean to have figures included in conference abstract?
Unless the submission guidelines/instructions suggest otherwise, they're not asking for a graphical abstract. They're asking for a figure(s) that illustrate the key results of the presentation (for instance, if your talk is "Correlations between A and B under Conditions X", you could include a graph of a against b).

Here's an example of a conference abstract with figures, taken entirely at random from the online programme of a recent ACS meeting.