Firstly, create a component with name detailPara check below command to create detailPara:
ng generate component detailPara
Or:
ng g c detailPara
Both are same after that paste your detailPara.html code to that detailPara component and same for BlockPara.html create component with below command:
ng generate component BlockPara
Or:
ng g c BlockPara
and paste BlockPara.html code to BlockPara component.
and finally use like this:
<div class="productPage">
<app-detail-para></app-detail-para> // check before pasting
<app-block-para></app-block-para> // check before pasting
</div>
Second Way
Using JavaScript
document.getElementById('detailPara').innerHTML =
'<object type="text/html" data="assets/detailPara.html" ></object>';
document.getElementById('blockPara').innerHTML =
'<object type="text/html" data="assets/BlockPara.html" ></object>';
<div class="productPage">
<div id="detailPara"></div>
<div id="blockPara"></div>
</div>
Here you can check Stackblitz.