#include<bits/stdc++.h>
#define ll long long
using namespace std;
const int N=1e6+5,M=5e3+5,inf=1061109567;
const ll INF=4557430888798830399;
int n,m,k;
int len[N],lsh[N],lle;
int stk[N+M],l,r,dis[N+M],tim[N];
ll dp[M];
char s[N],t[M];
int trie[N][30],tot;
void Init(){
	for(int i=0;i<=tot;++i) for(int j=0;j<26;++j) trie[i][j]=0;
	memset(dis,0x3f,sizeof(dis)),memset(tim,0x3f,sizeof(tim)),memset(dp,0x3f,sizeof(dp)),dp[0]=tot=dis[0]=0;
}
void Haiyi(){
	scanf("%d%d",&n,&k),Init();
	for(int i=1;i<=n;++i){
		scanf("%s",s+len[i-1]+1),len[i]=strlen(s+len[i-1]+1)+len[i-1],lsh[i]=len[i]-len[i-1];
		for(int j=len[i-1]+1,p=0;j<=len[i];++j){
			if(!trie[p][s[j]-'a']) trie[p][s[j]-'a']=++tot;
			p=trie[p][s[j]-'a'];
		}
	}
	sort(lsh+1,lsh+n+1),lle=unique(lsh+1,lsh+n+1)-lsh-1;
	for(l=r=0;l<=r;++l){
		if(stk[l]>=k){
			if(dis[stk[l]-k]>dis[stk[l]]+1) dis[stk[l]-k]=dis[stk[l]]+1,stk[++r]=stk[l]-k;
		}else for(int i=1;i<=lle;++i) if(dis[stk[l]+lsh[i]]<dis[stk[l]]+1) dis[stk[l]+lsh[i]]=dis[stk[l]]+1,stk[++r]=stk[l]+lsh[i];
	}
	for(int i=1;i<=n;++i)
		for(int p=0,j=len[i-1]+1;j<=len[i];++j){
			p=trie[p][s[j]-'a'];
			int t=((-len[i]+j)%k+k)%k;
			tim[p]=min(tim[p],dis[t]+(t+len[i]-j)/k);
		}
	scanf("%s",t+1),m=strlen(t+1);
	for(int i=0;i<=m;++i)
		for(int j=i+1,p=0;j<=m;++j){
			if(!(p=trie[p][t[j]-'a'])) break;
			if(tim[p]<inf) dp[j]=min(dp[j],dp[i]+tim[p]+1);
		}
	if(dp[m]<INF) printf("%lld\n",dp[m]);
	else puts("-1");
}
int main(){
	int T; scanf("%d",&T);
	while(T--) Haiyi();
	return 0;
}