Your question is about the impact of the triangular trade, also known as the Atlantic slave trade, on Europe. The triangular trade had several notable impacts on Europe, including massive profit opportunities, increased access to raw goods, more political power and colonization outside Europe, and the rise of the Industrial Revolution.
The triangular trade consisted of goods like textiles, mirrors, and guns from Europe being shipped to Africa, where they were exchanged for slaves. The slaves were then shipped to the Americas, where they were exchanged for raw goods like sugar, mahogany, and cotton. These goods were then shipped back to Europe.
Creating shipping lines to Africa and the Americas boosted Europe's shipping industry, providing jobs and income. As the amount of product being imported and exported from Europe grew, so did the number of ports, ships, and workers.
Doing business abroad helped create diplomatic relationships and opportunities to colonize countries outside Europe. European nations were able to more easily colonize African countries, for example, as they already had an established way to get supplies and transact business. The profit the countries received from the triangular trade helped them build their empires, which affected the political and social fabric of many countries both in and out of Europe.
A continuous stream of raw materials from the Americas and the profit generated by the slave trade together helped contribute to the rise of the Industrial Revolution. European factories formed to make more manufactured goods. This growth in technology and business ventures was also largely possible due to money received from the triangular trade, made by selling goods and selling slaves. Dr. Will Hardy explains:
The British cotton mills, which became the emblem of the "Industrial Revolution," depended on cheap slaved-produced cotton from the New World; cotton would have been more costly to obtain elsewhere. British consumers also benefited from other cheap and plentiful slaved-produced goods such as sugar. The profits gained from the slave trade gave the British economy an extra source of capital.
Without the triangular trade providing cheap raw materials, it's possible that the Industrial Revolution would have happened more slowly or focused on different types of manufactured goods in different areas of Europe. While the triangular trade isn't the only cause of the Industrial Revolution, it's likely it played its part.
One of the negative impacts of the triangular trade on European nations is the legacy of slave trading and colonialism. The awareness of slave trading also led to the rise of abolition movements in Europe that sought to end slavery.