Before seeking impact metrics, consider what you are trying to show, and take care to contextualize the information appropriately.
The recommendations linked below outline appropriate and ethical ways to use research impact data.
Considerations
There are different indicators to show impact at the article level, journal level, and researcher level. There are many more indicators and measures beyond the basic ones listed here - these are ones you are more likely to encounter.
Different databases are going to have slightly different citation numbers for the same article. This is because databases don't index exactly the same sources. Web of Science is more selective about the content that it indexes. Google Scholar tends to include more unpublished literature such as conference posters and proceedings. Lens.org uses open scholarly data.
Citation count is going to be less useful for brand new articles, as it takes time for papers to get cited. Citation norms also vary between fields.
