You might not find it for certain journals .. if there; you might find it in the Journal Info or under "Journal Metrics" .. regarding the scientific value; i cant say it's correlated as an indicator but not necessarily and it depends on may factors; mainly specialty, type of articles, publicity .. etc. 

In Spanish you can check this web:

https://www.recursoscientificos.fecyt.es/indices-de-impacto

Two are the main databases.

http://www.scimagojr.com/journalrank.php

http://admin-apps.webofknowledge.com/JCR/JCR?PointOfEntry=Home&SID=P12msdbA7s9EUGmLl1c

I think the Scopus/SJR is more comprehensive (Ref. H Index); Thomson Reuters'  ISI Web of Knowledge has become too narrow (They provide a snobbish, private, paid service).

No impact factor system is perfect, just in case.

Some answers may be found here, links follow.

https://www.researchgate.net/post/Any_suggestions_on_how_to_find_the_impact_factor_of_a_journal_and_its_rating_among_other_journals#567d7d1c5cd9e37d2c8b4567

http://wokinfo.com/products_tools/analytical/jcr/

https://www.researchgate.net/post/How_can_I_find_the_list_of_Impact_Factors_2015

Impact of any journal depend on individual test the way of reading habit in certain cases the habit of taking out the note from journal after reading the method of contemplation all this play in important part for the  readers .

Certain journal of the specialize subject & other than this certain journal cover quite good areas for reading & in certain cases it help the reader to develop ,it taste for new areas his liking & instinct are notice that the readers takes interest in such subject by reading various books on his topics which may contribute not for himself but also other readers interested in his topics.

Every reading is for individual liking & in certain cases the habit of reading becomes so much that the reader becomes addicted & workaholic & in this line what ever may be professional & career such person create such impression for his knowledge that he becomes the object of attraction among his friend ,relative including surrounding society .This is my personal opinion .