In reference to the patent: US8424138
Important to add that patents are territorial rights. Patents with No US-N,NNN,NNN are US patents with effect only to the US.
JP is for Japan, CA is for Canada, etc etc
When you see WO-YYYY-NNNNNN this is a patent application filed and published via the World Intellectual Property Organization (WIPO). They never mature to patents. They are only used as a centralized procedure from which the applicant chooses to enter territories and countries of his choice.
This is a US patent. The hint is the first two letters being "US". US patents only cover products made or sold in the US. Often US patents will have international equivalents. In Google Patents you often see a link for "Also published as" where you will find other patents and applications associated with the invention. I prefer The Lens for patent searching. There you will find a tab for "Family Info" which contains links to other associated patent documents. This link shows that there is no international equivalents for US8424138. Please note that although this patent is limited to the US, there are a lot of patents related to portable infant seats so you may need to consider other patents before marketing a product.