#include<bits/stdc++.h>
#define Gc() getchar() 
#define Me(x,y) memset(x,y,sizeof(x))
#define Mc(x,y) memcpy(x,y,sizeof(x))
#define d(x,y) ((m)*(x-1)+(y))
#define R(n) (rnd()%(n)+1)
#define Pc(x) putchar(x)
#define LB lower_bound
#define UB upper_bound
#define fi first
#define se second
using namespace std;using ll=long long;using db=double;using lb=long db;using ui=unsigned;using ull=unsigned long long;using pii=pair<int,int>;using LL=__int128;
const int N=1e6+5,M=5e3+5,K=14348907+5,mod=998244353,Mod=mod-1;const db eps=1e-9;const int INF=1e9+7;mt19937 rnd(time(0));
int Le,n,m,k,g[M],f[M],tg[M],dp[M],l[N],r[N];char s[N],t[M];
namespace Trie{
	int son[N][26],f[N],Ct;
	void Cl(){for(int i=1;i<=Ct;i++) Me(son[i],0),f[i]=0;Ct=1;}
	void Ins(string c,int Le){
		int x=1;
		for(int i=0;i<Le;i++) {
			c[i]-='a';if(!son[x][c[i]]) son[x][c[i]]=++Ct,f[Ct]=INF;x=son[x][c[i]];
			f[x]=min(f[x],f[(Le-i)%k]+(Le-i)/k);
		}
	}
}
void Solve(){
	int i,j;scanf("%d%d",&n,&k);Me(g,0x3f);Trie::Cl();
	l[0]=1;for(i=1;i<=n;i++){
		l[i]=l[i-1]+r[i-1];scanf("%s",s+l[i]);r[i]=strlen(s+l[i]);
		g[r[i]%k]=min(g[r[i]%k],r[i]/k+1);
	} 
	Me(f,0x3f);f[0]=0;Me(tg,0);
	for(i=0;i<k;i++){
		int Mi=-1;for(j=0;j<k;j++) if(!tg[j]&&(Mi==-1||f[Mi]>f[j])) Mi=j;
		for(j=0;j<Mi;j++) f[j]=min(f[j],f[Mi]+g[Mi-j]);
		for(j=Mi+1;j<k;j++) f[j]=min(f[j],f[Mi]+g[k-(j-Mi)]+1);
	}
	for(i=1;i<=n;i++) Trie::Ins(s+l[i],r[i]);
	scanf("%s",t+1);m=strlen(t+1);for(i=1;i<=m;i++) t[i]-='a';
	Me(dp,0x3f);dp[0]=0;
	for(i=0;i<m;i++){
		int x=1;
		for(j=i+1;j<=m;j++) if(Trie::son[x][t[j]]){
			x=Trie::son[x][t[j]];
			dp[j]=min(dp[j],dp[i]+Trie::f[x]+1);
		}else break;
	}
	printf("%d\n",dp[m]>=1e9?-1:dp[m]);
}
int main(){
	ios::sync_with_stdio(false);cin.tie(0);
	int t;
	scanf("%d",&t);
	// t=1;
	while(t--) Solve();
	cerr<<clock()*1.0/CLOCKS_PER_SEC<<'\n';
}