The ISI database id called now Clarivate Analytics, or you could refer to it as the Web of Science (WoS). If you would like to publish a paper in a journal that is indexed in this database, you could search this database, and observe the journals that are indexed there in your research area, observe what type of papers each journal published, and decide which one is suitable for your paper.
I don't think it is so difficult. There are four quartiles Q1, Q2, Q3, Q4 and depending on your work potential, you can submit in the most suitable quartile. Moreover, nowadays there are so many inter-disciplinary ISI journals where acceptance might be easier than the core journals.