The degree and transcript that the Chemist entry names, a reliable foreign-credential evaluation where the qualification was issued outside Canada, Mexico or the United States, and certified English translations of anything not in English. The employer’s letter is separate evidence and does not substitute for any of these.
Collect what the entry itself names
Three documents do most of the work. The first is the qualification named in the professional entry, in its original form, with the issuing institution identifiable on its face. The second is the transcript, which answers questions about field of study that a diploma cannot. The third, where the institution sits outside North America, is an evaluation by a recognised service establishing the North American equivalent of the credential; that evaluation answers an academic question and is not the same instrument as a translation. A document in French, or in any other language, going to USCIS needs a full English translation carrying the translator’s certification of accuracy, completeness and competence, and the translation should reproduce the original rather than tidy it.
Hypothetical example: a chemist in Roxton Pond who formulates adhesives and surface coatings for wood panels holds a chemistry degree from a university in Brazil and a letter from a wood-products manufacturer in the United States describing formulation and testing work on a new resin system. The evaluation is ordered first because it takes the longest and because everything else waits on its conclusion. While it runs, the employer is asked to name the professional entry relied on, describe the formulation deliverable, and identify the signatory. A resume is not one of the three documents and should not contradict any of them.