Advice on reusing images/illustrations from an AIMS paper
In general the authors will have assigned all copyright for figures to the journal upon submission/publication. I'm not familiar with the journal in question but it does not look to be any different from any I've ever seen (it has a title, volume, page number etc so is 'normally' citeable). If you wish to reproduce figures from any journal or other source then you need to contact the publisher. This is usually just a formality. 

In this case the contact page for the AIMS (https://www.aimsciences.org/common_news/column/contact) indicates you should get in touch with the Editorial Manager - editorial@aimsciences.org "Regarding the book/journal editorial process, book orders, Printed version claims, copyrights" (emphasis mine)