Generally, it takes about 4 to 6 months for backlinks to take effect on SEO. However, there are several other factors that can affect how long it takes for backlinks to take effect, including the quality of the backlinks, the website's authority, and the competition in your niche.
In order to get the most out of your backlinks, you'll need to make sure that you're also doing everything else right with SEO, including optimizing your website for keywords, publishing great content, and building high-quality links. If you're not seeing results after 4 to 6 months, then it might be time to revisit your SEO strategy and make some changes.