You can check the journal's official website. You can also confirm it by checking in the official website of Scopus and clarivate analysis (master journal list). Search using the ISSN number of the journal to check whether it is listed in Scopus or sci .

Dear Dominic Ndulue ,

As said by Janani Lekshmipathy look at the journal (homepage) of choice. However not all journals, predatory journals/hijacked journals) are honest about their indexing. You can check for Scopus indexing:

https://www.scopus.com/sources.uri?zone=TopNavBar&origin=searchbasic

Check for SCIE indexing (so journals with Clarivate impact factor):

https://mjl.clarivate.com/home

Best regards.

PS. SCImago is based on Scopus indexing (it is a sort of extra service linked to Scopus database):

https://www.scimagojr.com/

You can find out the list of Journal is indexed in Scopus, Scimago or Thompson Reuters from their web-sites.

You can find from the journal website, then cross check it to the list in Scopus, scimago or web of science website.