I have observed that in one of my published papers, there is a typo error. Instead of stating Figure 3 (b) and Figure 3 (c). The caption states Figure 3 d. Can please someone assist me, how can I fix it? Should I contact the journal editor?
The only possibility to correct this is with the help of the journal editor. Perhaps the journal can publish a correction in one of the next issues, or, if it is an online-only journal, they may even correct it in the file. However, this seems to be a minor error which does not change the main content of the paper. Therefore the editor may decide not to do anything. But you should not hesitate to contact the editor.
You should also contact the journal editor of your paper. Send a corrigendum to the journal. They are either able to fix it online or add it to the record.