I think something like this should do (with POST), but it seems to result in a server error:
?action=result&k={searchTerms}&t=and&o=none&s=0
The request headers:
POST / HTTP/2
Host: www.searchftps.net
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:88.0) Gecko/20100101 Firefox/88.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate, br
Content-Type: application/x-www-form-urlencoded
Content-Length: 56
Origin: https://www.searchftps.net
Connection: keep-alive
Referer: https://www.searchftps.net/
Cookie: ASP.NET_SessionId=zd5zimptynzpeqtom2h0cane; _ws5_u1=yes; _ws5_u12=yes; _ws5_u24=yes; _ws5_fs=yes; __gads=ID=bed19263439e7612-2258f1bf47c8007a:T=1621691772:RT=1621691772:S=ALNI_MaWlOgnEy3oYRR_6y2cf-LmhLKRzw
Upgrade-Insecure-Requests: 1
TE: Trailers
The request (for the query "test"):
action=result&args=k%3Dtest%26t%3Dand%26o%3Dnone%26s%3D0